The present invention relates to a dental prosthodontic apparatus and a method of securing and recovering a dental prosthesis. In more detail, the present invention relates to a dental prosthodontic apparatus which is provided with a gap for insertion of a prying instrument with surfaces formed in the gap against which the prying instrument bears for removing the prosthesis, the gap being formed by the lower margin of the prosthesis and the top surface of a riser which is fitted into the abutment on which the prosthesis is received, the fitted riser being sized so as to be slightly coronal to the patient's gum line.
Present dental practice tends toward the replacement of lost teeth with cylindrical or plate metal alloy abutments embedded in the bone of the mandible or maxilla to support the artificial tooth restoration. If extensive replacement of several teeth is needed, several abutments, alone or in conjunction with existing teeth prepared as abutments, are used to anchor the replacement prosthetic teeth.
In the last two decades, significant advances have occurred in both the abutments which are used for such replacements and in the methods used to implant the prosthodontic apparatus in the jaw. In one currently favored practice, titanium alloy abutment cylinders or plates are intimately installed in holes or slots drilled in the underlying bone of the jaw. Several months are allotted to allow the underlying bone to bond to the surfaces of the implant. For this reason, implant bodies are provided with at least one threaded hole on the crestal surface or edge. These holes are temporarily capped with a healing screw to prevent the invagination of soft tissue and/or bone into the internal threads. The soft tissue is sutured over the abutment until an intimate implant-bone bond is completed.
At the next surgical encounter, the soft tissue is resected and the healing screw is replaced with a metal alloy perimucosal extension of selectable height and emergence profile and the soft tissue is sutured around the base of this extension. This extension is usually bolted in place and prevented from rotating by locating pins and holes or internal and external matching hexagonal (or other regular polygonally-shaped) projections. These perimucosal extensions form the support for the artificial abutment(s) used to support the final prosthetic restoration.
The final prosthodontic restoration requires close mechanical mating between the abutment(s) and the internal aspect and underside of the prosthesis which is fitted on and cemented to the abutment. These closely matched parts often consist of telescoped, tapered conical surfaces requiring a tight, non-binding, "passive" fit on the abutment. This requirement demands inordinate precision from the laboratory technician and tests the technical skills of both the dentist and the laboratory technician. Parallel alignment of the axes of each abutment to prevent binding of the tapered fit is not easily achieved.
The methods and apparatus disclosed in Applicant's prior U.S. Pat. No. 5,564,928, in combination with an appropriate dental cement, yield a predictable, controllable technique for securing and, if necessary, retrieving the final restoration by providing a gap, or window, formed in the implant between the cemented prosthesis and abutment. The gap is formed of opposing surfaces on the prosthesis and the abutment with enough space between the surfaces to allow introduction of a prying instrument which can be manipulated to impose a force couple on the opposed surfaces. The dentist uses the prying instrument to apply even, measured force to gradually separate the prosthesis from the cement and gently remove it from the abutment.
Although the prosthodontic abutment described in Applicant's prior patent provides a satisfactory result, there is room for improvement. Specifically, because patients' gums are of varying thicknesses, the distance from the bone in which the abutment is implanted and the gum line varies from patient to patient and even in the same patient receiving multiple restorations. This variability creates a situation in which, even several sizes of the prosthodontic apparatus described in Applicant's Pat. No. 5,564,928 does not provide enough options to the restoring dentist to size the implant so that the gap between the prosthesis and the implant is positioned just coronal to the gum line. Even if several sizes of the prosthodontic apparatus described in that prior patent did provide enough variability, the mere fact that it must be provided in several sizes increases its cost and requires that the restoring dentist, lab or implant/abutment vendor keep a supply of parts of enough different sizes so as to provide the necessary variability.
It is, therefore, an object of the present invention to overcome this disadvantage by providing a dental prosthodontic apparatus which, even though provided in only several different sizes, is capable of being adapted for use in nearly every circumstance likely to be encountered by the restoring dentist or laboratory technician.
It is another object of the present invention to provide a dental prosthodontic apparatus with a gap between abutment and prosthesis the height of which can be changed relative to the patient's bone and soft tissue in which the abutment is sized to accommodate varying gum thicknesses.
It is another object of the present invention to provide a method of forming a gap in an implanted dental prosthodontic apparatus for allowing insertion of a prying instrument for retrieval of the prosthesis.
Yet another object of the present invention is to provide a method of mounting a dental prosthesis to an abutment connected to an implant placed in a jaw.
It is another object of the present invention to provide a dental prosthodontic kit having a plurality of risers of different heights for selection and insertion into a slot formed in an abutment so as to form a gap between the abutment having the riser of selected height therein and the prosthesis.
Other objects, and the advantages of the dental prosthesis of the present invention will be made clear to those skilled in the art by the following description of the presently preferred embodiments thereof.